Polyphase transformer for a variable speed constant frequency system

ABSTRACT

A transformer provides n phase outputs from m phase input voltages and comprises a core of magnetically permeable material having two shells connected by symmetrically arranged teeth. The number of teeth is a multiple of m, the number of phase voltages and of n the number of phase outputs. Wound on the teeth are m primary windings symmetrically arranged and each primary winding is energized by a phase voltage. n secondary windings are arranged on the core so that an output voltage is induced in each secondary winding and the secondary windings are positioned relative to one another in accordance with the desired phase angle separation of the outputs.

United States Patent 1191 Eckenfelder et al. 1 Jan. 16, 1973 154] POLYPHASE TRANSFORMER FOR A 3,118,070 1/1964 Gianola ..336/2l5 x VARIABLE SPEED CONSTANT 2,471,411 5/1949 Claesson ..336/215 x FREQUENCY SYSTEM 2,790,130 4/1957 Nyyssonen ..321/57 Inventors: Robert Charles Eckenfelder, Point Pleasant; Robert Frederick Kautz, Spring Lake; Albert William C0mpoly, Wall, all of NJ.

Assignee: The Bendix Corporation Filed: March 2, 1971 Appl. No.: 120,156

US. Cl. ..321/57, 336/5, 336/12, 336/215 Int. Cl. ..H02m 5/10 Field of Search ..336/5, 10,12, 214, 215; 321/57 References Cited UNITED STATES PATENTS Nyyssonen ..336/5 x Kunes ..336/5 Primary Examiner-Thomas J. Kozma Attorney-S. H. Hartz and Flame, Hartz, Smith & Thompson 5 7 ABSTRACT A transformer provides n phase outputs from m phase input voltages and comprises a core of magnetically permeable material having two shells connected by symmetrically arranged teeth. The number of teeth is a multiple of m, the number of phase voltages and of n the number of phase outputs. Wound on the teeth are m primary windings symmetrically arranged and each primary winding is energized by a phase voltage. 11 secondary windings are arranged on the core so that an output voltage is induced in each secondary winding and the secondary windings are positioned relative to one another in accordance with the desired phase angle separation of the outputs.

20 Claims, 5 Drawing Figures Pmmanm 15 I975 V 3.711 762 SHEET 1 (IF 4 YINVENITORS )QOBERT c, EC/(E/VFELDER ROBERT F. murz ALBERT w COMPOLV by I PATENTEDJAH 18 I973 3, 71 l, 762

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INVENTORS ROBE/PT C. EC/(ENFELDER POBERTF KAUTZ AL BE/Qf COM/50L) fz/fi' PATENTEDJAN 16 I975 3.711.762

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Rossm' C. ECKENFELDER ROBERT F. Kaurz 41.55 7' 14 CON/POLY POLYPHASE TRANSFORMER FOR A VARIABLE SPEED CONSTANT FREQUENCY SYSTEM The invention relates to transformers and more particularly to polyphase transformers.

In variable speed constant frequency systems used heretofor, in order to provide a three phase output by adding vectorially four three phase voltages separated in phase by four separate three phase transformers were used and the transformers were large, cumbersome and heavy and the assembly was difficult to mount. The present invention overcomes this difficulty by using a single polyphase transformer which is relatively light in weight and simple to wind.

The transformercomprises a core of magnetically permeable material having two shells connected by symmetrically arranged teeth. The four three phase voltages referred to in the example above comprise 12 voltages and the core includes 12 teeth.

A primary winding is wound on each tooth and each primary winding is energized by a phase voltage. A secondary winding is provided on the core for each phase of the output and the secondary windings are arranged so that an output voltage is induced in each secondary winding and the secondary windings are positioned relative to one another in accordance with the phase angle separation of the outputs.

One object of the present invention is-to provide a polyphase transformer which may be used to combine any number of phase voltages and provide an output of 30 2 any desired phase of phases.

Another object is to provide a single polyphase transformer which is relatively small, light and easily mounted for combining a plurality of phase voltages.

The foregoing and other objects and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawings wherein three embodiments of the invention are illustrated by way of example. It is to be understood, however, that the drawings are for the purpose of illustration only and are not a definition of the limits of the invention, reference being had to the appended claims for this purpose.

In the drawings,

FIG. 1 is a front view of a polyphase circular transformer constructed according to the invention and shows the arrangement of the primary and secondary windings on the core.

FIG. 2 shows the flux induced in the transformer core of FIG. 1 by energizing a single primary winding by one of the phase voltages.

FIG. 3 shows the arrangement of the secondary windings on the core in the second embodiment of the invention, the primary windings being arranged as shown in FIG. 1.

FIG. 4 is a perspective view of a third embodiment of the invention, and

FIG. 5 is a top view of the embodiment shown in FIG. 4.

In the drawings, a novel transformer constructed according to the invention is shown in FIG. 1 for combining twelve voltages forming the four three phase voltages described above. The transformer comprises a circular laminated core 1 of magnetically permeable material with a central aperture 2. Core 1 has a continuous outer shell 5 and a continuous inner shell 7 positioned concentrically and connected by twelve equally spaced teeth 9 disposed substantially radially therebetween and spaced 30 from one another. Apertures 11 are formed in the core between the teeth. A primary winding 13 is wound on each tooth 9 through the adjacent apertures 11 and has leads 15, 17 for connecting the primary winding to one of the phase voltages. The transformer shown in FIG. 1 is designed to be energized by the 12 voltages. The voltages may comprise four three phase voltages separated in phase by 15 and one phase voltage of each three phase voltage is applied to windings l3 identified in FIG. 1 as A-l, B- 1, C-1 and D-l. A second phase voltage of each three phase voltage is applied to windings identified as A-2, 13-2, 02 and D-2 and the third voltage of each three phase voltage is applied to windings identified as A-3, 13-3, C-3 and 0-3.

When the primary windings 13 are energized in this manner the flux in the teeth does not vary by more than $20 percent and the flux in the outer shell and in the inner shell is a summation of the flux from all twelve teeth and is approximately twice the flux in one tooth so that for balanced flux density in the core the inner shell and outer shell cross sectional area should be about twice the cross sectional area of one tooth. The flux in the shell is cyclic in nature and follows the input frequency. The flux pattern in the core from a single winding is quite complex and is approximated in FIG.

The distribution of the flux is determined by reluctances of the magnetic paths in the core. The total flux due to one primary winding is:

1 mm f and the reluctance is:

For reluctances in parallel as in the case of the 12 phase transformer the total reluctance is:

The flux in the core induces voltages in secondary windings 19, 21 and 23 in FIG. 1 which provide a three phase output comprising phases X, Y and Z separated by Secondary winding 19 includes coils 25, 27 wound on outer shell 5 through apertures'll separated 120 from one another and the coils are connected by a lead 29. Secondary winding 19 has a neutral terminal N, connected to coil 27 and an output terminal connected to coil 25 for providing the X phase of the output. Secondary winding 21 includes coils 31, 33 wound on outer shell 5. Coil 31 is wound through the same aperture 11 as coil 25 and coil 33 is wound through an aperture 11 spaced 120 from coil 31 and the coils are connected by a lead 35. Secondary winding 21 has a neutral terminal N connected to coil 31 and an output terminal (1),, connected to coil 33 for providing the Y phase. Secondary winding 23 includes coils 37, 39 wound on outer shell 5. Coil 37 is wound through the same aperture 1 1 as coil 33 and coil 39 is wound through the same aperture 11 as coil 27 so that coils 37 and 39 are also spaced 120 from one another. The coils are connected by a lead 41. Secondary winding 23 has a neutral terminal N, connected to coil 37 and an output terminal 1b, connected to coil 39 for providing the Z phase. Neutral terminals N,, N, and N are connected together when secondary windings 19, 21 and 23 are connected in Y configuration.

In a second embodiment of the invention shown in FIG. 3, each secondary winding 43, 45 and 47 is wound on the core through apertures 11 separated by 120 and subtend the teeth and portions of the core therebetween. With this arrangement, coils 43 and 45 are wound through the same aperture and coils 45 and 47 are wound through the same aperture and coils 43 and 47 are wound through the same aperture as shown in FIG. 3. Coil 43 has a neutral terminal N and an output terminal 4). for providing the X phase of the output. Secondary winding 45 has a neutral terminal N and an output terminal for providing the Y phase of the output and secondary winding 47 has a neutral terminal N and an output terminal for providing the Z phase. Neutral terminalsN N and N may be connected together when secondary windings 43, 45 and 47 are connected in Y configuration. Secondary windings 43, 45 and47 provide a three phase output in which phases X, Y and Z are separated by 120.

In athird embodiment of the invention shown in FIG. 4, the transformer shown therein has a triangular laminated core la of magnetically permeable material with a substantially central aperture 3a therein. Core 1a is formed of an upper triangular shell 5a and a lower triangular shell 7a positioned parallel toone another and connected by 12 symmetrically arranged teeth 9a with apertures 11a between the teeth.

Each shell is assembledfrom a number of stampings and each shell comprises a triangular portion and onehalf each tooth 9a. Teeth 9a are bent at substantially right angles to the triangular portion and the ends of the teeth are machined. Two shells are assembled with the ends of adjacent teeth in engagement with one another and the shells are secured together by a bolt through aperture 3a.

A primary winding 13a is wound on each tooth 9a through adjacent apertures 11a and has leads 15a, 17a for connecting the primary winding to one of the phase voltages. r

If four three phase voltages are used as in the embodiment of FIGS. land 3, then one phase voltage of each three phase voltage is applied to windings 13a identified in FIG. 4 as A-l, B-l, C-l.and D-l. A second phase voltage of each three phase voltage is applied to windings identified as A-2, B-2, C-2 and 13-2 and the third phase voltage of each three phase voltage is applied to windings identified as A-3, B-3, C-3 and D3.

Secondary windings 19a, 21a and 23a are wound on the core through apertures 110 at the corners of the core and subtend the teeth and portions of the core therebetween similarly to theembodiment shown in FIG. 3. The transformer shown in FIG. 4 operates in the same manner as the transformers shown in FIGS. 1

and 3.

' It will be observed that output power for each phase is derived in part from all 12 input phases so that power factor loading is no great problem to anyone input phase. The inherent filtering ability of polyphase iron cores and vector summation of the 12 phase input voltages produces an output voltage with little harmonic content. Square wave inputs across the primary windings produce sine wave output voltages in the secondary windings with no additional filtering.

While the description and drawings are directed to a 12 phase input and a three phase output any number of input and output phases can be accommodated using the polyphase technique described herein. The primary windings preferably are symmetrically distributed on the core and the secondary windings are arranged on the core relative to one another in accordance with the phase angle separation of the outputs. The number of teeth should be equal to or a multiple of m, the number of input voltages and a multiple of n the number of phase outputs. This arrangement permits m symmetrically distributed primary windings to be wound on the teeth of the core for energization by the input voltages and permits n secondary windings to be positioned relative to one another on the core to subtend a number of teeth corresponding to the desired phase angle separation of the outputs.

What is claimed is:

l. A transformer for providing n phase outputs from m phase voltages where m a 2n, comprising a core of magnetically permeable material having two shells connected by spaced teeth therebetween, the number of teeth being a multiple of m the number of phase voltages and of n the number of phase outputs, m primary windings wound on the teeth and each primary winding being energized by a phase voltage, the primary windings being arranged on the teeth to induce flux in the core corresponding to the vector sum of the voltages, and n secondary windings wound on the core and each secondary winding subtending a number of teeth equal to the number of teeth divided by n the numberv of secondary windings and each tooth being subtended by only one secondary winding, the secondary windings being relatively positioned on the core in accordance with the desired phase angle separation of the outputs and each secondary winding providing an output COT-r responding to the vector sum of the flux in the portion of, the core subtended by the winding.

2. A transformer as described in claim 1 in which the core is circular and the shells are separated by the teeth.

3. A transformer as described in claim 2 in which the teeth are positioned substantially radially and the shells are concentric.

4. A transformer as described in claim 1 in which the number of teeth equal m the number of phase voltages and a primary winding is wound on each tooth.

5. A transformer as described in claim 1 in which the core has apertures between the teeth and the primary windings are wound about the teeth through the apertures.

6. A transformer of the kind described in claim 1 in which the shells are continuous and magnetic flux is induced in the shells by energization of the primary windings by the phase voltages.

7. A transformer as described in claim 2 in which the cross sectional area of the one shell is substantially equal to the cross sectional area of the other shell.

8. A transformer as described in claim 7 in which the induced magnetic flux in the shells is substantially equal. 4 v

9. A transformer of the kind described in claim 7 in which the shell cross sectional area is substantially twice the cross sectional area of a tooth so that the flux density is balanced.

10. A transformer as described in claim 9 in which the induced magnetic flux in the shells is approximately twice the flux in any one tooth.

11. A transformer as described in claim 2 in which the secondary windings are wound on the core about one of the shells and are arranged in accordance with the phase separation of the outputs.

12. A transformer as described in claim 1 in which the secondary windings are wound on the core and subtend a number of teeth corresponding to the phase angle separation of the outputs.

13. A transformer as described in claim 5 in which the core is circular and the secondary windings are wound about one of the shells through the apertures and the windings are arranged on the core in accordance with the phase angle separation of the outputs.

14. A transformer as described in claim 5 in which the core is circular and each secondary winding is wound on the core through two apertures angularly spaced from one another in accordance with the angular phase separation of the outputs and subtend the teeth therebetween.

15. A transformer as described in claim 5 in which the core is triangular and each secondary winding is wound on the core through two apertures angularly spaced from one another in accordance with the angular phase separation of the outputs and subtend the teeth therebetween.

16. A transformer as described in claim 1 in which the shells are substantially triangular and are positioned substantially parallel to one another and are separated by the teeth.

17. A transformer as described in claim 16 in which the teeth are positioned substantially perpendicularly to the shells.

18. A transformer as described in claim 16 in which the shells are substantially identical.

19. A transformer as described in claim 18 in which the induced magnetic flux in the shells is substantially equal.

20. A transformer as described in claim 1 in which the primary windings are symmetrically distributed on the core. 

1. A transformer for providing n phase outputs from m phase voltages where m > OR = 2n, comprising a core of magnetically permeable material having two shells connected by spaced teeth therebetween, the number of teeth being a multiple of m the number of phase voltages and of n the number of phase outputs, m primary windings wound on the teeth and each primary winding being energized by a phase voltage, the primary windings being arranged on the teeth to induce flux in the core corresponding to the vector sum of the voltages, and n secondary windings wound on the core and each secondary winding subtending a number of teeth equal to the number of teeth divided by n the number of secondary windings and each tooth being subtended by only one secondary winding, the secondary windings being relatively positioned on the core in accordance with the desired phase angle separation of the outputs and each secondary winding providing an output corresponding to the vector sum of the flux in the portion of, the core subtended by the winding.
 2. A transformer as described in claim 1 in which the core is circular and the shells are separated by the teeth.
 3. A transformer as described in claim 2 in which the teeth are positioned substantially radially and the shells are concentric.
 4. A transformer as described in claim 1 in which the number of teeth equal m the number of phase voltages and a primary winding is wound on each tooth.
 5. A transformer as described in claim 1 in which the core has apertures between the teeth and the primary windings are wound about the teeth through the apertures.
 6. A transformer of the kind described in claim 1 in which the shells are continuous and magnetic flux is induced in the shells by energization of the primary windings by the phase voltages.
 7. A transformer as described in claim 2 in which the cross sectional area of the one shell is substantially equal to the cross sectional area of the other shell.
 8. A transformer as described in claim 7 in which the induced magnetic flux in the shells is substantially equal.
 9. A transformer of the kind described in claim 7 in which the shell cross sectional area is substantially twice the cross sectional area of a tooth so that the flux density is balanced.
 10. A transformer as described in claim 9 in which the induced magnetic flux in the shells is approximately twice the flux in any one tooth.
 11. A transformer as described in claim 2 in which the secondary windings are wound on the core about one of the shells and are arranged in accordance with the phase separation of the outputs.
 12. A transformer as described in claim 1 in which the secondary windings are wound on the core and subtend a number of teeth corresponding to the phase angle separation of the outputs.
 13. A transformer as described in claim 5 in which the core is circular and the secondary windings are wound about one of the shells through the apertures and the windings are arranged on the core in accordance with the phase angle separation of the outputs.
 14. A transformer as described in claim 5 in which the core is circular and each secondary winding is wound on the core through two apertures angularly spaced from one another in accordance with the angular phase separation of the outputs and subtend the teeth therebetween.
 15. A transformer as described in claim 5 in which the core is triangular and each secondary winding is wOund on the core through two apertures angularly spaced from one another in accordance with the angular phase separation of the outputs and subtend the teeth therebetween.
 16. A transformer as described in claim 1 in which the shells are substantially triangular and are positioned substantially parallel to one another and are separated by the teeth.
 17. A transformer as described in claim 16 in which the teeth are positioned substantially perpendicularly to the shells.
 18. A transformer as described in claim 16 in which the shells are substantially identical.
 19. A transformer as described in claim 18 in which the induced magnetic flux in the shells is substantially equal.
 20. A transformer as described in claim 1 in which the primary windings are symmetrically distributed on the core. 